ABSTRACT:Solid-state structures of comb-like polyacrylates (PAx) and polymethacrylates (PMx) having crystallizable n-octadecyl side chains and their blends with n-octadecanoic acid (Cl8) have been investigated by means of differential scanning calorimetry and X-ray diffraction methods. It is concluded that n-alkyl side chains of comb-like polymer cocrystallize with low-molecular-weight Cl8 by incorporation of Cl8 into hexagonal crystalline lattice. In the case of amorphous PMx, the addition of Cl8 can induce a formation of crystalline domain by the cocrystallization with the side chain. Differences in the crystallization behavior, such as fractions of crystallized methylene units and effects of thermal history, between PAx and PMx are found to be considerably large. These results are explained by the difference in the segmental mobility of main chain.KEY WORDS Comb-Like Polymer/ n-Octadecanoic Acid/ Cocrystallization / X-Ray Diffraction/ DSC Measurement / n-Alkyl Side Chain / Differences in solid-state nature between side chain and main chain in comb-like polymers are anticipated to give a wide variety of phases, structures, and morphologies, for example, those in side-chain liquid crystalline polymers 1 and rigid-rod polymer with flexible side chains. 2 -4 Comb-like polymers, which have crystallizable long n-alkyl side chains being attached to amorphous main chain, are known to pack into layered structure with alternating crystalline side-chain region and amorphous main-chain region in the solid state. 5 -13 Plate and Shibaev 6 studied these comb-like polymers extensively. X-Ray diffraction profile for such polymer has an intense reflection corresponding to the Bragg spacing d of 4.2 A, which suggests a formation of hexagonal crystalline lattice of n-alkyl side chain. There also exists a reflection in smaller angle region, which is considered to originate from the layered structure. The repeating distance of crystalline-amorphous layer can be obtained by the diffraction angle of this reflection. Plate et al. 6 observed striking difference in the diffraction patterns and layer spacings between comb-like polyacrylates and polymethacrylates. In order to interpret this difference, they proposed two models for chain packing: two-layer structure and one-layer structure for respective polymers. In the former model, the side chains are extended on both side of the main chain and these polymers pack closely because of the flexibility of the main chain. In the latter structure, the disordered packing of the end groups of side chains occurs because of the increased bulkiness of the main chain, and the polymer chains are arranged with a shift toward the extended side-chain axis. Later, Hsieh et al. 9 proposed a new structural model for the solid state poly(n-octadecyl methacrylate), where the side-chain crystallites are formed by intercalating side chains pointing in opposite directions. Although the detailed solid-state structures of these comb-like polymers have not been clarified as yet, the layered structure with the...

ABSTRACT:Crystalline-amorphous layered structure constructed by comb-like poly[(methyl acrylate)-stat-(n-octadecyl acrylate)]s (PAx), which have crystallizable n-alkyl side chains and amorphous main chain, has been investigated by X-ray diffraction method. Small-angle X-ray scattering profiles of PAx and its blends with n-octadecanoic acid (Cl8) varies with the change of !//main, which is defined as the ratio of the number of then-alkyl side chain and Cl8 molecule to that of the main chain -CH2-CH-unit. When !//main is smaller than 0.71, the layer spacing obtained from diffraction angle of a sharp peak at small-angle region gradually decreases with an increase of !//main· In the region of 1/fmain=0.73-0.89, a broad peak coexists with the sharp peak, and locates at smaller angle region than the sharp peak. When !//main is larger than 1.0, i.e., blends of poly(n-octadecyl acrylate) (PA 100) with C 18, a newly appeared sharp reflection can be observed at further smaller angle. These complicated variations in layer spacing are interpreted by three packing models, which are named as Interdigitating Form, End-to-end Form, and disordered End-to-end Form, respectively. Differential scanning calorimetry measurements for PA!00/Cl8 blends also suggest the existence of another crystalline form induced by the addition of Cl 8. In the blends of PAI00 with n-tetradecanoic acid, the chain length of which is shorter than Cl 8, the structural transformation observed in PA!00/Cl8 system can not be recognized.KEY WORDS Comb-Like Polymer/ n-Alkyl Fatty Acid/ Poly(n-octadecyl acrylate)/ Layered Structure / X-R«y Diffraction / Layer Spacing/ Packing Manner/ Comb-like polymers, in which crystallizable long nalkyl side chains attach to amorphous main chain, have been extensively studied as reviewed by Plate and Shibaev. 1 In these polymers, the side chains are known to crystallize in solid state irrespective of their tacticity of main chain. X-Ray diffraction and differential scanning calorimetry (DSC) measurements suggest the formation of hexagonally-packed crystalline lattice of n-alkyl chain. In the X-ray profile at small-angle region, there exists an intense reflection, which is considered to originate from alternating crystalline-amorphous layered structure constructed by the side-chain-crystallized layer and main-chain-segregated amorphous layer as shown in Figure 1. The domain spacing of the layered structure, d, can be obtained by the diffraction angle of this reflection. Plate et al. 1 • 2 reported striking difference in the diffraction pattern and layer spacing d between comb-like polyacrylates and polymethacrylates. In the diffractogram of poly(n-octadecyl acrylate), a relatively broad reflection was observed at small-angle region and its spacing was larger than 40 A, and in that of poly(n-octadecyl methacrylate), a sharp reflection was observed at the spacing of ca. 30 A. In order to interpret this difference in X-ray profiles, they proposed two chain-packing models: two-layer structure and one-layer structure for respectiv...

The solid state morphology of the main-chain liquid crystal BB-6 polyester was studied by the small angle X-ray scattering (SAXS) method. The BB-6 polyester forms isotropic, smectic A, and crystal phases in the order of decreasing temperature; thereby its crystallization is taking place from the smectic A phase. The SAXS for the crystalline specimens prepared by cooling the isotropic melt at a rate of 10 °C min-1 shows the well-defined reflection maxima which are attributable to the stacked lamellar structure. The lamellar spacings are distributed around 250 Å so that an appreciable number of chain foldings are included in a chain. The lamellar size is increased by annealing the crystal like in other crystallizable polymers. In contrast, it is not essentially altered by annealing the smectic A phase. The results show that the chain foldings exist at a thermodynamic equilibrium in the smectic A phase. The correlation length between the chain foldings is assumed approximately to be 250 Å, which corresponds to 15 times the length of the repeat unit.

Colloidal crystal assembly film was prepared by using monodispersed colloidal particles of cross-linked random copolymer of methyl methacrylate and ethyl acrylate prepared by soap-free emulsion polymerization. The colloidal crystal film exhibited structural color when swollen with ethyl acrylate monomer. The structural color was maintained even after polymerization of the swelling monomer and cross-linker, suggesting the colloidal crystalline order was successfully fixed and embedded in the matrix of poly(ethyl acrylate) elastomer. Stretching deformation of the structural colored elastomer induced a sensitive change to shorter wavelength color. Peak wavelength of the UV-vis absorption spectrum of the stretched elastomer revealed an excellent proportional relationship with film thickness. In the swollen colloidal crystal film, ethyl acrylate was absorbed in the colloidal particle; therefore, poly(ethyl acrylate) chain should be penetrating into the colloidal particle after the polymerization of the matrix elastomer. This interpenetrated polymer network structure was considered to be effective for the rubber-like elasticity and sensitive strain-responsive color-changing phenomena of the structural colored elastomer.

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